Chisel



gamma Jan. 28, 1936. H. E. POLLARD CHISEL Filed Oct. 26, 1954 as w. O gwzi/ fi \S 4w N NW I k Patented Jan. 28, 1936 IETE STATEE FATENT OFFICE CHISEL nois Application October 26, 1934, Serial No. 750,200

2 Claims.

My invention relates to power operated reciprocating tool devices in general, but more especially to power operated chisel devices of the type comprising a barrel in which the tool is located and 5 in which it reciprocates responsive to blows directed against it by a piston located in the barrel and operated, as for example, by compressed air; together with means cooperating with the tool for restricting reciprocation thereof and preventing it from dropping out of the body of the device when the device is not operating and being driven therefrom when no resistance to outward movement of the tool is presented, as for example when the tool is disengaged from the work either intentionally or by glancing therefrom.

It is desirable, particularly where the toolactuating mechanism is of large size and great power and a relatively small tool, such as a chisel, is used therewith as is found desirable in practice, to provide the tool of such form that the metal thereof shall be so distributed as to cause the tool to withstand to as great a degree as possible, fatigue under the great stresses to which it is subjected in use, and particularly where the tool is so manipulated as to exert a prying action on the work, as for example in the removal of the heads of rivets, it being one of my objects to provide a tool of such form as to present the maxi mum resistance to such stresses commensurate with the amount of metal forming the tool, thereby utilizing, to the maximum extent, the metal of the stock from which the tool is made.

Furthermore, in devices of this character and comprising. a sleeve in which the tool is located, with cooperating shoulders on the sleeve and tool to resist outward movement of the tool as above referred to, it is desirable that the cooperating surfaces of these shoulders be of relatively large extent and so disposed as not to result in such localization of spreading stresses upon the sleeve that it will be unduly subjected to fracture, it being another of my objects to provide for such distribution of the shoulders, in a construction in which the cutting edge of the tool is of a length substantially equal to the diameter of the stock from which the tool is made and the shoulders thereof are made by removing portions of the stock, with the minimum reduction of cross section of the tool relative to the diameter of the stock in a direction normal to the cutting edge and the most effective distribution of the metal in the tool; and other objects as will be manifest from the following description.

Referring to the accompanying drawing:

Figure 1 is a broken view in longitudinal sectional elevation of a device embodying my invention.

Figure 2 is a side view of the chisel shown in Fig. 1 and viewing it in a direction normal to Fig. 1.

Figure 3 is a similar view of the sectional retainer sleeve forming a part of the illustrated device, with the tool positioned therein, the structure being viewed normal to Fig. 1; and

Figure 4, a section taken at the line ll on Fig. l and viewed in the direction of the arrows.

Referring to the particular illustrated embodiment of my invention, the barrel of a pneumatic chisel device, in connection with which I have chosen to illustrate my invention and such as is commonly provided, is represented at 5, the compressed-air-operated piston (not shown) of the device reciprocating in this barrel to deliver blows to the chisel represented at 6 constructed in accordance with my invention, and extending into, and reciprocable in, the outer open end of the barrel 5.

Surrounding the inner end of the chisel 6 and extending into the open end of the barrel 5, is a sleeve 1 forming one section of the retaining means for the chisel. The bore of this sleeve is inwardly tapered, as represented at 8, and cooperates with the inner tapered end portion 9 of the chisel to form stop means limiting inward movement of the chisel when pressed against the work to the position shown in the drawing, in which position the inner extremity of the chisel extends inwardly beyond the inner end of the sleeve '5 as shown.

The outer end of the sleeve 1 is annularly flanged as represented at H] at which portion it laps the outer end of the barrel 5 thereby forming the stop means limiting inward movement of the sleeve.

The retaining means also comprises a sleeve section it surrounding the chisel 6 and disposed in alinement with the sleeve section 7, the bore l 2 of the sleeve I I being of general rectangular shape in cross section with its corners rounded, thereby providing a circumferential series of straight shoulders l3 shown as equidistantly spaced and preferably chamfered as illustrated.

The chisel 6 is provided toward its inner end with a circumferential series of inset shoulders 5G shown as four in number and equidistantly spaced around the tool, these shoulders, which are preferably chamfered as shown, opposing the shoulders IS, the arrangement and proportions of the parts described being such as shown that when the chisel is in its innermost position as tions being held on the barrel by a housing memthe barrel 5, forces the chisel 6 at its cutting edge ber l6 secured at its inner end on the outer threaded end ll of the barrel 5 andprovided atits outer end with an inwardly extending annular flange l8 between which and the flange I5 on the sleeve I l, a buffer H], as for example of rubber, is interposed, the outer end of the sleeve H preferably extending loosely through the open' end of the housing member I6.

In the use of the device the operator, grasping 20 against the work, as for example the head of a rivet to be cut off, and the piston above referred to delivers the desired impacts against the inner end of the chisel for severing the head from the shank of the rivet.

When there is no resistance by the work to outward movement of the chisel under the impacts produced by the piston, as for example when the device is started into operation before applying it to thework, or should the chisel glance from the rivet, or the device is continued in operation following the cutting off of the head of the rivet, the chisel 6 is driven at its shoulders. M against the shoulders N3 of. the sleeve II which transmits the force exerted by the chisel, to the sleeve II and in turn to the buffer l9 backed by the flange !8 of the housing member H5.

The chisel 6 is formed, as for example by machining and forging operations, from round steel stock, and in accordance with the preferred illustrated embodiment of the invention, the shoulders M, in the direction crosswise of the tool are disposed at angles to each other of approximately 90, thereby forming two diametrically opposed sets of the shoulders, and the cutting edge 2!! in the direction of its length is disposed at an angle to each of the shoulders M of. approximately 45, the cutting edge 20 being provided of a length substantially equal to the diameter of the tool at the portion 2| thereof and corresponding with' the original diameter of the stock from which the chisel is made; In the forging of the chisel to the shape shown the stock is reduced in thickness from each shoulder M to the opposite end of the 'chisel along the surfaces represented at 22 but only to an extent sufflcient to permit the chisel to be inserted through the inner end of the sleeve 5 i to position therein.

It will be understood from the foregoing that by disposing the cutting edge 20 relative to the shoulders II; as described it is possible to cause the chisel to be provided of such form, as shown,

' as to utilize to the maximum extent the metal of the stock from which the chisel is formed, in

the resisting of the stresses to which the chisel is subjected in use, thereby prolonging the life.

of the chisel. Furthermore, by thus forming the chisel the thickness thereof normal to the cutting edge is greatly increased as compared with a chisel in which the cutting edge is parallel with the stop shoulders of the chisel in the direction nipulates the tool device to exert a prying action on the head of a rivet during the operation of removing the head.

The feature of providing the shoulders 13 arranged around the longitudinal axis of the sleeve ii as shown is of advantage, as compared with a structure in which only two shoulders, diametrically opposed, are provided, inasmuch as spreading stresses produced on the sleeve i l by the engagement of the tool therewith, are distributed around the sleeve, thereby reducing likelihood of fracture of the sleeve.

While it is preferred that the shoulders M be provided of the number and arrangement as shown, I do not wish to limit my invention thereto as they may be provided of a different number and arrangement. Thus, by way of example, two only of the shoulders M with only two reduced portions 22 extending in registration therewith, the shoulders being diametrically opposed, may be provided, and with the cutting edge 2t disposed at an angle to these shoulders certain advantages of my invention may be obtained.

Furthermore, various other modifications and alterations of the construction shown may be I made within the spirit of nry invention, and therefore, I do not wish to be understood as intending to limit it to the structures as shown and above described. a a

What I claim as new, and desire to secure by Letters Patent, is:

1. A tool of the class described having a substantially cylindrical portion at one end and a cutting edge at the other end, four shoulders between said portion and the cutting edge of the mounting portion between said portion and the cutting edge of the tool. adapted for impact with a mounting sleeve or the like, said shoulders being within the imaginary extension of said mounting portion, and said cutting edge being of a width substantially equal to the lateral dimension of said mounting portion and lying in a longitudinal plane passing through diagonal corners of the tool formed by the said shoulders.

HUGH E. POLLARD. 

